The invention relates to a single wheel suspension of a rear wheel, the same being steerable, at least minimally, by way of an actuator, of a vehicle having two wheel paths (a double-track vehicle). The wheel carrier of the suspension is guided by a longitudinal control arm which extends substantially in the longitudinal direction of the vehicle, as well as by two transverse control arms which extend at least approximately in the transverse direction of the vehicle, and which are positioned in different planes when viewed in the longitudinal direction of the vehicle, and do not intersect with each other. The other ends of the transverse control arms, opposite the wheel carrier, are connected either directly or indirectly to the vehicle construction in a manner allowing at least minimal articulation, and the other end of each transverse control arm is attached to the wheel carrier by a bolt or the like via a rubber bearing or a joint which has at least a minimal degree of rotary freedom. Reference is hereby made particularly to U.S. Pat. No. 4,709,935, as well as to EP 0 052 663 B1 and DE 38 27 039 A1 as relevant prior art.
EP 0 052 663 B1 discloses what is also called a central pivot axle among specialists, and this is characterized by an advantageous kinematic behavior, particularly when used in a driven wheel, and is also more advantageous than the known, so-called semi-trailing arm axle. DE 38 27 039 A1 shows one option for making it possible for a wheel guided in such a manner to be minimally steered. In this case, the toe angle of this wheel can be adjusted by use of an actuator which suitably engages with a bearing of the longitudinal control arm, said bearing being positioned on the vehicle construction. Such a minimally steerable axle is shown in its entirety in the closest prior art, U.S. Pat. No. 4,709,935. This known arrangement requires additional construction space, not only at the position of the longitudinal control arm bearing on the vehicle construction, but also in the immediate proximity of the longitudinal control arm, for the horizontal articulation thereof (in the transverse direction of the vehicle). Depending on the form of the vehicle construction in this region, such constructed space may not be available.
In the present case, the problem is that of detailing how it is possible to design a single wheel suspension and/or vehicle axle in a manner allowing minimal steering of the same, while preserving the fundamental kinematic and elastokinematic properties of such a wheel suspension, without a greater need for constructed space in the end region of the longitudinal control arm closest to the vehicle construction.
The solution to this problem is characterized in that the longitudinal control arm is also attached to the wheel carrier by way of the two named bolts or the like, in each case via one rubber bearing or at least one joint (the bearing or joint may be referred herein simply as a joint) having at least one minimal degree of rotary freedom, in such a manner that the wheel carrier is able to swivel relative to the longitudinal control arm, at least minimally, about a swivel axis which runs substantially vertically and which is formed by this rubber bearing or joint. The resulting degree of rotary freedom of the wheel carrier is bound by a tie rod element which is connected to the wheel carrier via an articulated joint, wherein the tie rod element can be moved at least sectionally in the transverse direction of the vehicle by way of the actuator.
According to the invention, as in the case of DE 38 27 039 A1 described above, the wheel carrier is not only able to swivel at least to a small degree with respect to the two transverse control arms, but also with respect to the longitudinal control arm, about a swivel axis which runs substantially vertically, such that—in contrast to this known prior art—the longitudinal control arm itself does not need any freedom of movement relevant for the present invention in the transverse direction of the vehicle. The swivel axis (also called a kingpin axis or rotary steering axis) in this case is formed by two joints or rubber bearings, or the like, via which the wheel carrier is connected to the longitudinal control arm.
According to the invention, the latter two joints or rubber bearings are attached with the same bolts or the like with which the joints or rubber bearings of the two transverse control arms are attached. The two joints or the like are preferably press-fitted into suitable recesses of the wheel carrier and each fastened by a bolt or the like on the longitudinal control arm, wherein a rubber bearing which is also press-fit into a transverse control arm is also fastened on the longitudinal control arm by way of the bolt or the like. By means of this particularly advantageous arrangement or connection, not only are the space requirements minimized, but also the assembly process is kept as simple as possible, because only two bolted connections—namely via the two bolts—are required to connect the wheel carrier to the longitudinal control arm and the two transverse control arms.
By way of example, two so-called flanged bearings can be configured on the wheel carrier, which extend substantially in the vertical direction and at least approximately in the transverse direction of the vehicle, and therefore (each) describe a plane which is at least approximately perpendicular to the longitudinal direction of the vehicle. The two flanged bearings can lie in a common plane or in planes which are only minimally separated from each other. By way of example, a pivot joint (cf. for example DE 10 2004 017 639 A1) can be press-fit by its joint housing (“head”) into each such flanged bearing, the pivot pin of which extends substantially horizontally, at least approximately in the longitudinal direction of the vehicle, and also passes through at least one flange or one mounting link of the longitudinal control arm, and furthermore accommodates a rubber bearing press-fit into one of the two transverse control arms, which is supported, for example with a spacer in between, by the flange (and/or by the mounting link) of the longitudinal control arm, and is held by a nut screwed onto the free end of the pivot pin and/or is tensioned as a whole against the longitudinal control arm flange (or mounting link). In this case, the pivot pin of the pivot joint therefore forms the bolt named in the independent claim, and said swivel axes describe the center point of the joint ball of the two pivot joints.
As an alternative, instead of such a pivot joint given by way of example, conventional rubber bearings or ball joints (“ball bushing joints”), or in general joints having at least one minimal degree of rotary freedom, meaning that the same extends over a sufficient angular range, can be suitably inserted into the flanged bearing of the wheel carrier, said flanged bearing likewise being given only by way of example. The joints then each are fastened on the longitudinal control arm and/or tensioned against the same by use of a bolt, preferably a screw, and optionally with a spacer in-between, together with a rubber bearing or joint of one of the two transverse control arms.
It is hereby expressly stated again that the flanged bearing of the wheel carrier, described above, is only one possible example of an embodiment of the present invention. Alternative embodiments are possible, of course; what is essential is that the wheel carrier is connected to the longitudinal control arm via two joints or rubber bearings or the like, the same forming a swivel axle which runs substantially vertically, in each case by way of a bolt or the like, wherein each bolt furthermore serves the purpose of attaching one of the transverse control arms on the longitudinal control arm via a further joint or rubber bearing or the like. The arrangement of each rubber bearing or joint on the bolt in this case can have one or two link points, meaning that instead of the named flanged bearing, two mounting links positioned next to each other can be included, each of which describe a plane which is at least approximately perpendicular to the longitudinal axis of rotation, between which a rubber bearing, for example, is tensioned by use of the named bolt. Of course, the longitudinal control arm can also be fastened to the wheel carrier in an articulated manner, by two joints being inserted in a suitable manner into the longitudinal control arm, wherein each of the joints is fastened to the wheel carrier by use of a bolt, and wherein one of the two transverse control arms is fastened to the wheel carrier by use of the same bolt.
The swivel axis and/or the joints or the like which form the same, wherein the wheel carrier according to the invention is able to pivot about the same relative to the longitudinal control arm, creates and/or create a degree of freedom which according to the invention is bound by a so-called tie rod element which can be moved at least sectionally, in the transverse direction of the vehicle, by way of an actuator (servomotor). During such a movement, the articulation point of the tie rod element on the wheel carrier describes a (short) semicircular curve, the mid-point of which is on the swivel axis. Due to external forces applied to the vehicle wheel attached in a rotatable manner on the wheel carrier, relative movements between the wheel carrier and the actuator, the same attached at a suitable point on the wheel suspension or on the vehicle construction near the wheel suspension can occur, for which reason the tie rod element should be articulated on the wheel carrier and/or on a movable adjuster element of the actuator in such a manner that at least the adjuster element of the actuator, and preferably also the tie rod element itself, is kept substantially free of transverse forces and torques which are not oriented about the axis of the adjuster element or the tie rod element. In this way, damage to the actuator resulting from such external forces (wheel cornering forces, longitudinal wheel forces, and vertical forces) is ruled out.
In principle, one dedicated actuator can be functionally assigned to each wheel carrier of the rear axle, said actuator then preferably being mounted on the longitudinal control arm, or a single actuator can be configured for the two wheel carriers of the rear axle, said actuator being arranged substantially in the center and mounted on an axle carrier, or alternatively on the vehicle body, by way of example. In principle, the mounting of the actuator can be rigid or itself articulated. The latter configuration presents the possibility of the adjuster element of the actuator, which can be a spindle which can be moved longitudinally by an electric motor (as an actual actuator) via a suitable gearing (as a component of the actuator), being kept isolated from transverse forces and torque applied to this spindle, wherein the same can result from forces acting externally on the wheel carried by the wheel carrier. In this case, the articulated mounting of the actuator must of course be designed in such a manner that the movement of the actuator adjuster element is transmitted to the tie rod element connected to the same without modification.
Forces which are applied to the wheel carried by the wheel carrier have already been mentioned, the same being absorbed as usual via the two transverse control arms and the longitudinal control arm, as well as a suspension spring element on the vehicle body. According to the design of the joints between the wheel carrier and the longitudinal control arm, said joints forming said swivel axis, it may be practical to include a further support, the same being preferably slightly elastic, between the wheel carrier and the longitudinal control arm, wherein the further support would then need to have a degree of freedom for the swivel movement of the wheel carrier relative to the longitudinal control arm, the swivel movement created by the actuator. In order to therefore support the wheel carrier on the longitudinal control arm in a more robust and stiffer manner, without placing loads on the moving adjuster element of the actuator, an additional load path, which is preferably in front of the swivel axis when viewed in the direction of travel, can be configured or implemented between the wheel carrier and the longitudinal control arm. This load path particularly is able to function in the vertical direction, because this is the direction of the largest loads, and because the two other load paths leading through the joints (or rubber bearings) which form the swivel axis are relieved of load by way of such an additional load path in the form of a further support.
In summary, multiple embodiments, which are not exhaustively detailed below, therefore exist for embodying the connection between the actuator—and more precisely the actuator adjuster element—and the wheel carrier, said connection forming the degree of rotary freedom of the wheel carrier about the swivel axle.
One embodiment is the connection, mentioned above, via a tie rod element, which is arranged by way of example in the manner of a stabilizer bar connecting link, wherein a transmission of force is only possible in one (single) direction—particularly the longitudinal direction of the tie rod element. In this case, the actuator (formed as mentioned above by a gearing with an electric motor, for example) can be rigidly connected to the longitudinal control arm. By means of an arrangement of the actuator effectively inside the longitudinal control arm, the actuator requires only a small amount of constructed space, but as a result the strength of the longitudinal control arm can initially be lowered for the necessary passage of the actuator adjuster element, which can then be compensated for by a careful incorporation of the actuator housing into the longitudinal control arm as a load-bearing structure. According to an alternative embodiment, the actuator can be a component of the tie rod element, and therefore can be mounted, as mentioned above, in an articulated manner, on the longitudinal control arm, for example (in this case, each wheel of the vehicle rear axle has its own actuator), or directly or indirectly on the vehicle construction with an axle carrier or the like in-between, wherein it is possible in this case to also configure an actuator, which is preferably arranged centrally, for both wheels of the rear vehicle axle, in addition to two actuators, each of which is dedicated for one wheel.
A further embodiment for binding the degree of freedom, the same realized by the swivel axis, of the wheel carrier, with respect to the longitudinal control arm, consists of a tie rod element as explained above, and the support, the same also described above, of the wheel carrier with respect to the additional element which implements the longitudinal control arm. In addition to the tie rod element, the segment of the wheel carrier which is close to the connection of the tie rod element is connected to the longitudinal control arm via such an additional element, which at least has the degree of freedom necessary for the steering movement or pivot movement of the wheel carrier. The wheel carrier is connected more stiffly to the longitudinal control arm via this additional element, and load is removed from the two force paths or load paths via the joints which form the swivel axle. Of course, the additional element can also be connected to the housing of the actuator and/or supported on the same, particularly if the same is designed as a structure of the longitudinal control arm which also is load-bearing, as mentioned above. As an advantageous implementation which is figuratively illustrated as a potential embodiment, and is also described below, the tie rod element can be constructively integrated into the additional element, meaning into the additional support between the wheel carrier and the longitudinal control arm.
The invention is described in greater detail using two embodiments, of which a first (without an additional element as named in the previous paragraph) is illustrated in FIGS. 1-4, while FIG. 5 shows a detail, shown enlarged in FIG. 5a, of a second embodiment, having such an additional element.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.